Color matching apparatus



Nav. 26, 1946. J. L. MICHAEL SON 2,433,741

COLOR MATCHING APPARATUS Filed D60. 13, 1939 Y 9 I O g 83 5 Q I 52 lllLllF- 48 AMPLIFIER Inventor:

Jesse L. Michaelson,

Patented Nov. 26, 1946 COLOR MATCmG arraaa'rus Jesse L. Michaelson, Schenectady, N. Y assignor to General Electric Company, a corporation of New York V Application December 13, 1939, Serial No. 309,013

7 Claims. (Ci. 88-14) 2 is emitted from the light source. The cam 62 is arranged to be rotated through the gearing as from the shaft 39 at a 1:1 speed ratio. That part of each monochromatic beam which passes the lower openings 68 passes the lens i3 and is reflected by the rocking mirror i into one or the other of the two windows it or it of the integrating sphere 16 depending upon the position of the mirror. The mirror is shown mounted upon with the accompanying drawing, and its scope m the rock shaft 'i'l having the arm it which enwill be pointed out in the appended claims. gages the flicker cam i l mounted on the shaft The single figure of the drawing is a perspec- H2. The integrating sphere is provided with two tive view of apparatus adapted for use in producwindows opposite the windows it and it which ing spectrophotometric curves of light reflected are adapted to be covered by the objects 8t and from two surfaces. single light source is emhi which may be considered sample and standployed which is dispersed into its separate wave ard the refiectances of whose surfaces are to be lengths and those wave lengths successively procompared. Opposite another window 82 of the jected upon the surfaces of two flat objects which sphere is the photoelectric device 36, the armay be termed a sample and a standard, the rangement being such that the light received light reflected therefrom being received by a by the device is limited to that transmitted by' photoelectric device. The output of that de the window from the interior of the sphere. vice controls the tracing of the reflectance curves Coordination of movement of the various movby a cathode ray tube. able parts of the apparatus is secured by inter- The light from the light source or lamp @5 is connecting the main or drive shaft 38 with the collected by the lens 58 and illuminates the slit cam F t rough the gear 53 and with the 61 which is for the purpose of providing the decams as through the shaft 39 and the 1:1 bevel sired degree of purity in the monochromatic gears 83. The shaft is also connected with the light beam finally received by the light sensitive flicker cam shaft it through e Shaft the member 36. The slit comprises two vertical 1:1 bevel gearing 55 and the 1:2 bevel gearplates each having two light openings 58 there- 30 mg 56.

' in. The two plates are moved simultaneously The output of the photoelectric device at after in opposite directions by .the. cams 69 on the being amplifled by the amplifier 65 is applied to shaft 39, each plate being held against its cam the vertical deflection plates d6 of the cathode by a spring shown above the plate. .The rockray tube 8. The horizontal deflection plates M ing prism 'ltl has a reflecting rear face whereof the tube are connected with the battery 68 by monochromatic light is directed back on the through the potentiometer 69 having the oscilslit. Arranged in front of the prism is the lating arm 5t controlled by the cam 5'2 on the lens H which renders parallel the rays of light shaft 313. During the interval at which the varireceived from the slit Bl. On this lens there is ous wave lengths are directed upon the object formed an image of the filament of the lamp 65. 80 the cathode ray tube will draw a curve shown The light reflected by the prism ill passes again for example by C which is the reflectance curve through the lens H which images the upper light of that object. Likewise, during that interval openings 68 of the slit 61 on the slit in the at which the various wave lengths are directed vicinity of the lower light openings 68 thereof. upon the object 8|, the cathode ray tube will As the prism is rocked the monochromatic light it draw the curve represented by D which is the of the various wave lengths passes the lower openreflectance curve of that object. The apparatus ings and is controlled thereby. The prism is is operated at such a speed that the two curves mounted on the shaft 26 having the arm 21 which are drawn so rapidly that they appear to the obengages the wave length .cam 29 on the shaft server as being continuous.

30. Between the lens H and the slit 6! I have In order that the observer may better be able shown the cam 52 for controlling the transto distinguish one curve from the other particumission of the monochromator in such a manner larly when the curves lie close to each other I as to give a uniform deflection of the beam of may cause one curveto have some distinguishthe cathode ray tube 3 over the whole wave ing characteristic, for example one curve may be length range of the prism ll! when white light caused to have short lines projecting therefrom at intervals. For this purpose I have shown at 85 a device for producing small intermittent voltage impulses connected in circuit with the photoelectric device. In order that only one curve may be so marked the arm II by which the mirror is rocked is provided with the comtacts 88 which during one halt oi the rotation of the flicker cam H are separated and during the other halt rotation are in contact and are connected to short circuit the impulse generator 85.

The operation of the apparatus is 'as follows: During each short interval when the mirror arm 18 is in engagement with that portion of the cam ll having the larger radius whereby the light beam dispersed and reflected by the prism is reflected by the mirror. 1 toward the object 80, the prism is rocked by the cam 29 from one limiting position thereof to the other so that the object receives monochromatic light successively oi the various wave lengths of the light emitted by the lamp. This projection of monochromatic light 01 various wave lengths on the sample is produced by the scanning action of the 'lower opening 88 in the right-hand plate as a result of the relative motion of the opening and the spectrum which is produced by the rocking oi the prism 10. During this interval also the potentiometer arm 50 is moved from one limiting position thereof to'the other by the cam 52, the slit 81 is adjusted to produce the desired purity of the monochromatic light reaching the object 80, and the cam 42 is varied. Owing to the 1:2 ratio of the gears 56 between the drive shaft 30 and the shaft 54 and the 1:1 ratio oi the gears 55 between shaft 54 and the flicker cam shaft I2, the contact arm 50 is moved back and forth across the potentiometer. 49 twice during each complete cycle of operation of the scanning means; once when the arm 18 is in engagement with the high portion of the cam II and once when it is in engagement with the low portion. As a result of the varying potential differences applied between the deflecting plates 46 and between the deflecting plates 41 of the cathode ray tube, during the interval in which arm 18 is on the high portion of the cam the beam thereof is caused to trace on the end of the tube the spectrophotometric curve due to the reflectance of theobject 80 since the displacement of the beam horizontally is proportional to the movement of prism 10 which changes the wave length and the displacement of the beam vertically is proportional to the various factors comprising the product of the light intensity, monochromator transmission, the response of the photoelectric device, and

the characteristics of the voltage amplifier and,

the cathode ray tube. The curve so traced may, for example, be that represented at C. In like manner while the arm 18 is in engagement with that part of the cam I I having the smaller radius the light beam is reflected by the mirror I on the object 8| while the prism is rocked from one extreme position to the other whereby the 4 flectance curve of the one object with respect to that of the other object, the moving parts 01 the apparatus being operated at such a speed that the two curves appear to be continuous.

It is sometimes desirable to observe the spectrophotometric curve of the light transmitted by an' object rather than that oi the light reflected thereby. In that case I employ identical objects 80 and BI, preferably white, to cover the lower windows or the integrating sphere and in front of one of the windows, either 14 or 15, I arrange the object whose transmission is to be observed. Such an object is represented by dotted lines at 83.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a photoelectric device arranged to receive light reflected from a plurality of objects having different reflectance, means for alternately illuminating said objects each for a short interval, means operative during each .interval for limiting the illuminating light to a group oi. adjacent wave lengths and for varying the ,wave lengths comprising said group through a predetermined range, and means operating synchronously with said wave length varying means and controlled by the output of said photoelectric device for producing a plurality of curves each representing the energy reflected by one of said objects at the various wave lengths.

2. In combination, an integrating sphere having openings for receiving light reflecting materials, a photoelectric device associated with said sphere, a source of light, means for reflecting light therefrom for short intervals alternately on said materials, means for dispersing light from said source and directing the wave lengths of the dispersed light successively on said reflecting means during each of said intervals and a cathode ray tube having deflecting means responsive to the output of said device and to the position of said directing means.

3. A method of comparing a plurality of color specimens which includes the steps of creating a spectrum, passing successive bands of said spectrum first over one of said specimens and then over another of said specimens, impressing the light reflected by said specimens on a photosensitive surface to produce for each specimen an electrical value of a magnitude varying with the magnitude of the wave length of light reflected by said specimen, amplifying said value produc- .ing a beam of radiant energy, projecting said direction in response to said amplified value, pc-

curve D is drawn on the end of the cathode ray tube.

From the foregoing it is seen that during a complete cycle 01 operation oi the scanning means light from the scanned spectrum is projected on both specimens, 1. e., the sample and i the standard and that separate curves representing the reflectance of each specimen appear onthe screen of the cathode ray tube. One is able to observe any difference in the form of the reriodically effecting relative movement .between said beam and said screen at an angle to said first direction, and synchronizing said last mentioned movement with the cycle of production of said electrical value, the period of said cycle approximating the period of persistence of vision.

4. An instrument for evaluating color comprising, in combination, means for projecting the spectrum of a light beam, means for supporting a plurality of color specimens, means including a scanning device for projecting first on one of said specimens and then on another successive bands of monochromatic light from saidspectrum, a photoelectric device so positioned with respect to said color specimens as to receive therefrom light reflected thereby, whereby there is created by. said photoelectric device electrical values of varying magnitudes, the variations of which correspond respectively to the variations of light intensity reflected by said specimens,

means for cyclically operating said scanning device, means connected to said photoelectric device for amplifying said values, a screen, electrical means for projecting a beam on said screen to produce a visible trace thereon as the beam and screen move relative to one another, means responsive to said amplified values for effecting relative movement between said beam and said screen in one direction, cyclically operated means for effecting relative movement between said beam and said screen at an angle to said first direction whereby said beam forms visible curves on said screen representative of said electrical values, and means for synchronizing said lastmentioned means with said scanning device operating means, the period of operation of said scanning device operating means and of said cyclically operated means approximating the period of perisistence of vision.

5. An instrument for evaluating color comprising, in combination, means for projecting the spectrum of a light beam, means for supporting a plurality of color specimens, means including a scanning device for projecting first on one of said specimens and then on another successive bands of monochromatic light from said spectrum, a photoelectric device so positioned with respect to said color specimens as to receive therefrom light reflected thereby, whereby there is created by said photoelectric device electrical values of varying magnitudes. the variations of which correspond respectively to the variations of light intensity reflected by said specimens, means for cyclically operating said scanning device, means connected to said photoelectric device for amplifying said values, a screen, electrical means for projecting a beam on said screen to produce a visible trace thereon as the beam moves relative to the screen, means responsive to said amplified values for deflecting said beam in one direction, cyclically operated means for 'deflecting said beam at an angle to said first direction, the frequency of curve producing operation of said last-mentioned means being so related to the frequency of said scanning device operating means that the trace on said screen forms a plurality of superimposed curves equal in number to the number of specimens being evaluated, and means for synchronizing said lastmentioned means with said scanning device operating means.

6. An instrument for evaluating color comprising, in combination, means for projecting the spectrum of a light beam, means for supporting a plurality of color specimens, means including a scanning device for projecting first on one of said specimens and then on another successive vice, means connected to said photoelectric de- I vice for amplifying said values, a screen, electrical means for projecting a beam on said screen to produce a visible trace thereon as the beam moves relative to the screen, means responsive to said amplified values for deflecting said beam in one direction, cylically operated means for deflecting said beam at an angle to said first direction, the frequency of curve producing operation of said last-mentioned means being a multiple of that of said scanning device operating means equal to the number of specimens being evaluated, whereby the trace on said screen forms a plurality of superimposed curves equal in number to the number of specimens being evaluated, and means for synchronizing said last-mentioned means with said scanning device operating means.

7. An instrument for evaluating color comprising, in combination, means for projecting the spectrum of a light beam, means for supporting a plurality of color specimens, means including a scanning device for projecting first on one of said specimens and then on another successive bands of monochromatic light from said spectrum, a photoelectric device so positioned with respect to said color specimens as to receive therefrom light reflected thereby, whereby there is created by said photoelectric device electrical values of varying magnitudes, the variations of which correspond respectively to the variations of light intensity reflected by said specimens, means for cyclically operating said scanning device, means connected to said photoelectric device for amplifying said values, a screen, electronic means for projecting a beam on said screen to produce a visible trace thereon as the beam moves relative to the screen, a pair of deflecting plates connected to said amplifying means and responsive to said amplified values for deflecting said beam in one direction, cyclically operated means including a second set of deflecting plates associated with said first-mentioned plates and with said electronic beam projecting means for deflecting said beam at an angle to said flrst direction, and means for synchronizing said last-mentioned means with said scanning device operating means, the period of operation of said scanning device operating means and of said cyclically operated means approximating the period of persistence of vision.

JESSE L. MICHAELSON. 

